Alkylation of aryl hydrocarbons



Patented July 8, 1947 UNITED STATES PATENT OFFICE Carlisle M. Thacker, Highland Park, and Ralph C. Swann, Skokie, Ill., assignors to The Pure Company, Chicago, Ill., a corporation of o No Drawing. Application December 13, 1943, Serial No. 514.161

16 Claims.

This invention relates to the synthesis of alkylated aromatic hydrocarbons and more particularly to the synthesis of alkyl benzenes from alkyl mercaptans or sulfides and benzene or other aromatic hydrocarbons.

We have discovered that aromatic hydrocarbons react with alkyl mercaptans and alkyl sulfides in the presence of a Friedel-Crafts catalyst, such as anhydrous aluminum chloride or ferric chloride to form alkylated aromatic hydrocarbons and hydrogen sulfide. Reaction takes place at temperatures ranging from approximately 50 C. to approximately 400 C., but preferably in the range of 100 to 200 C. At lower temperatures longer contact times are necessary than are required at higher temperatures. Reaction takes place at atmospheric or at super-atmospheric pressure. In order to prevent formation of polyalkyl aromatics, it is desirable to maintain a molal excess of benzene or other aromatic hydrocarbons to alkyl mercaptans or sulfides in the reaction. The higherthe mole ratio of benzene to alkyl mercaptan or sulfide, the higher the yield of the mono-alkyl benzene based on the alkyl mercaptan or sulfide charged to the reaction. Ratios of benzene to alkyl mercaptans from 2 to 1 to a ratio of 14 to l and ratios of benzene to alkyl sulfides from 4-t0 1 to a ratio of 28 to 1 give satisfactory results in the preparation of monoalkyl benzenes. The metal halide catalyst should be present in the reaction mixture in amounts of not less than 0.1 mole per mole of mercaptan and may be present in amounts up to 2 moles or more per mole of mercaptan.

The metal halides used to catalyze the reaction are commercial anhydrous halidesj No special precautions are observed in handling to prevent absorption of traces of moisture from the air.

Contact time between the reactants and catalyst may vary from a few minutes to twenty hours or more. Good yields may be obtained at a reaction time of thirty minutes to six hours.

The process may be batch, semi-continuous or continuous. In batch operation, the desired quantities of reactants and catalyst may be placed in a closed reaction vessel, preferably provided with a mixing device. The reaction mixture is maintained at the desired temperature for the required period of time, after which the contents are taken from the reaction vessel, the metal halide complex decomposed by acid hydrolysis and the resulting products fractionated to recover alkyl benzene or other alkylated aromatic hydrocarbons, as well as unreacted aromatic hydrocarbons and mercaptan or sulfide.

reaction vessel.

Yields of alkyl benzene up to approximately of theoretical may be obtained in accordance with our invention using reaction periods of moderate duration in a batch operation.

In semi-continuous operation, benzene or other aromatic hydrocarbon and alkyl mercaptan or sulfide may be intermittently charged to the reaction vessel, with corresponding alternate separation of products, for a given initial charge of catalyst until the catalyst phase is substantially exhausted. Since the catalyst phase containing the catalyst and its various complexes with the reactants is of greater density and higher boiling point than the reactants and desired products, the upper layer, or product phase, may be separated from the catalyst phase by mechanical means without disturbing the lower catalytic complex phase, or by stripping ofi the upper product phase by distillation leaving the lower catalyst phase to be used for catalyzing the reaction of another charge of reactants.

In continuous operation a, series of reactors may be provided in which metal halide or metal halide complex is contacted serially with a stream of benzene and alkyl mercaptan, the reactants passing serially through the reaction vessels containing catalyst of gradually increasing activity. The aluminum chloride and ferric chloride form complexes with the reactants which may be used as catalytic material until the activity thereof is exhausted.

In order to demonstrate our invention, a series of runs was made using aluminum chloride and ferric chloride in the synthesis of ethyl benzene from benzene and ethyl mercaptan. Data in connection with the runs are set forth in the following table.

The temperatures given in the table represent the average of temperatures which were maintained during the reaction period given under the heading Time at stated temperature. The figures given under Total contact time include the entire time that the reactants were in the The figures given under the heading Contact time during cooling represent the period elapsed from the time heating of the reaction vessel was discontinued until it was opened.

The maximum and residual pressures given in the table represent the highest pressure obtained during the reaction and the pressure in the reaction vessel at the time it was opened. In runs 21--23 an initial pressure was imposed on the reaction mixture by means of nitrogen gas.

The yields of ethyl benzene are based on the theoretical yield'possible from the quantity of ethyl mercaptans charged to the reaction vessel. Ethyl benzene in the reaction mixture was determined by carefully fractionating the reaction prepared in the same manner as the ethyl benzene by substituting the corresponding mercaptan for ethyl mercaptan. As previously pointed out, temperatures in the range of 100 C. to 200 products in the laboratory and using a combina- 5 C. are preferable where mono-alkyl benzene is tion of boiling points and. refractive indexes to desired. Higher temperatures tend toward the determine the content of ethyl benzene in the formation of poly-alkylated benzenes and polymixture. alkylated benzenes also tend to form with higher Contact Time in Hours Pressurein Lbaper Sq.In. Yield 01 Run No catalyst gaxfiig M81815)! iiiltg At Stated During T213? w fi m Total Temp. Cooling Max. End Initial of theoretical 1 3 0.5 23.5 1.5 17.3 105 12 Atm 153 50 1 3 0.5 223 5.0 13.3 110 20 Atm 154 70 0.5 3 0.5 22.5 0.3 12.5 115 17 Ann 150 54 0.125 3 0.5 24.3 510 13.3 120 15 Atm 151 35 0.25 4.5 0.5 23.3 0.5 10.3 150 15 Atni 200 37 0.5 3 0.5 24.0 0.5 18.6 250 Atm 202 55 0.5 1 0.5 21.3 5.0 13.3 130 55 Atm 151 27 0.5 2 0.5 23.3 5.0 14.0 125 30 Atm 140 51 0.5 0.5 23.5 0.0 13.5 114 12 Atm 152 05 0.5 7 0.5 23.3 0.0 13.3 102 12 Atm 151 84 0.5 3 0.5 22.0 5.0 12.5 238 110 10051,..-" 153 45 0.5 3 0.5 23-0 0.0 13.3 350 200 200N,..... 152 55 0.5 3 0.5 22.5 0.0 12.5 477 200 3001s,-.." 151 40 3 0.5 22.5 0.0 125 140 Atm 152 45 8:: 3 0.5 22.3 0.0 11.7 155 25 Atm- 151 0.5 3 0.5 24.5 5.7 15.3 ,115 10 Atm 151 43 From the table it will be seen that good yields ratios of the alkyl mercaptan to benzene 1n the are obtainable at both 150 and 200 C. and that mixture. Therefore, when it is desired to prepare yields of ethyl benzene increase with the mole 3 mono-alkyl benzenes molal ratios of benzene to ratio of benzene to ethyl mercaptan. (See runs mercaptan of 2 to 1 or higher should be used. 30, 29, 26, 32 and 31.) Increase in reaction time It will be seen, therefore, that we have disalso improves the yield. (Runs 24 and 25.) It is covered a new method for preparing alkylated also apparent from the table that yields of ethyl aromatic hydrocarbons. benzene increase as the mole ratio of aluminum 35 We claim: chloride to ethyl mercaptan increases. (Runs 25, 1. The method of synthesizing alkyl benzenes 26 and. 28.) The initial pressure or the maximum which comprises reacting benzene with a compressure in the reaction vessel do not appear to pound selected from the group consisting of allmaterially afiect the yield of ethyl benzene. (See phatic mercaptans and alkyl sulfides at a temruns 26, 21, 22 and 23.) 4 perature of approximately 100-400 C. in the The results obtained clearly show anhydrous presence of a Friedel-Crafts catalyst for a period ferric chloride or mixtures of anhydrous ferric of time suiiicient to permit formation of a subchloride and anhydrous aluminum chloride to be stantial quantity of alkyl benzenes. excellent catalysts for the reaction. 2. The method of synthesizing alkyl benzenes The runs recorded in the table were all made which comprises reacting benzene with an allin a steel bomb having a capacity of 840 cc., havphatic mercaptan at temperatures of approxiing a glass liner. In making the runs, benzene, mately 100-200 C. in the presence of a Friedelcatalyst and alkyl mercaptan were weighed into Crafts catalyst for a period of time sufficient to the liner and immediately put into the bomb and permit formation of a substantial quantity of the bomb top tightened. The bomb was then alkyl benzenes. heated to the desired temperature and the tem- '3. The method of synthesizing alkyl benzenes peratures, times and pressures recorded. After which comprises reacting benzene with an allthe desired period of heating, heat was turned oil phatic mercaptan at temperatures of approxiand the bomb allowed to cool until it had reached mately 100-200. C. in the presence of not less a temperature of about 25 C. The bomb was than about 0.1 mole of Friedel-Crafts catalyst then dismantled and the contents of the liner per mole of mercaptan for a period of time sumwere again weighed. The contents of the liner cient to permit formation of a substantial quanwere then poured into a. separatory funnel and tity of alkyl benzenes.

agitated with cold water acidified with acid in 4. The method of synthesizing ethyl benzene order to decompose the catalyst complex. The 00 which comprises contacting amixture oi! benzene resulting liquid was then washed with caustic and ethyl mercaptan at temperatures of apsoda solution followed by water and then filtered. proximately 150-200 C. with a Frieda-Craft 5 resulting S p e as then a y d r ethyl catalyst for a period of time suflicient to permit enzene. m Anhydrous hydrogen chloride may be used in 22 2 of a substantial quantity of alkyl hen (fmmunction w1tn the aluminum chloride and/or The method of synthesizing ethyl benzene erric chloride. ,The presence of small amounts which com 1 t ti m t f b of hydrogen chloride in thereaction mixture pr ses con nga x ureo enzene tends to increase the yield of anwl benzene and ethyl mercaptan with not less than 0.1 mole drogen chloride may be used in amounts ranging of Friedel-Crafts catalyst per mole of ethyl merfrom 0.01 mole to 1.0 mole per mole of metal Captain at a temperature of approximately ha11de 200 C. for a period of time suficient to permit 1:; will b nd r t d th t monoor 1 formation of a substantial quantity of alkyl alkylated benzenes, other than ethyl benzene, as e es. for example methyl and propyl benzenes, may be M h according to Claim 2 i which th molal ratio of benzene to mercaptan in the reaction mixture is greater than 1:1.

7. Method according to claim 1 in which the Friedel-Crafts catalyst is anhydrous aluminum chloride.

8. Method in accordance with claim 1 in which the Friedel-Crafts catalyst is anhydrous ferric chloride.

9. vThe method of synthesizing alkylated aromatic hydrocarbons which comprises contacting a mixture of benzene and an aliphatic mercaptan in which the molal ratio of benzene to mercaptan is greater than 1:1 with a catalyst selected from the group consisting of anhydrous aluminum chloride and anhydrous ferric chloride at a temperature of approximately 100-200 (J. for a period of time suiiicient to permit formation of a substantial quantity of alkyl benzenes.

10. Method in accordance with clairn 9 in which the moial ratio of benzene to mercaptan is within the limits of 2:1 to 14:1.

11. Method in accordance with claim 9 in which the catalyst is present in an amount not less than about 0.1 mole per mole of mercaptan.

12. Method in accordance with claim 4 in which the catalyst is anhydrous aluminum chloride.

13. Method in accordance with claim 4 in which the catalyst is anhydrous ferric chloride.

14. The method of synthesizing ethyl benzene which comprises contacting a mixture of benzene and ethyl mercaptan in a molal ratio within the limits of 2:1 to 14:1 with not less than 0.1 moleper mole of mercaptan of a catalyst selected from the group consisting of anhydrous aluminum chloride and anhydrous ferric chloride at a temperature of approximately 150-200 C. and maintaining the reaction mixture at reaction tem- 6 perature for a period not less than approximately 30 minutes. N

15. The method of synthesizing mono-alkylated benzenes comprising contacting benzene and an alkyl mercaptan for a period of time not less than about thirty minutes in a ratio of 2 to 14 moles of benzene to 1 mole of mercaptan at a temperature of IOU-200 C. in the presence of a catalyst selected from the group consisting of anhydrous aluminum chloride and anhydrous ferric chloride in an amount not less than about 0.1 mole per mole of mercaptan.

16. Method in accordance with claim 15 in which the reaction period is approximately onehalf to six hours and the catalyst is present in an amount of approximately 0.1 to 2 moles per mole of mercaptan.

CARHSLE M. THACKER. RALPH C. SWANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Tsukervanik et al., "Condensation of A- hols-Aluminum Chloride HI," Chem. Abst. 31: 5779 (1937). Jour. Org. Chem., vol. 4, pa e 48 (1 page only). (Patent Oflice Library (1939).) 

